According to the National Institute on Drug Abuse (NIDA), marijuana is the most commonly used illegal drug in the United States. The main ingredient that provides an altered state, or high, is called THC. THC, or delta-9-tetrahydrocannabinol, is a chemical that passes though the lungs into the bloodstream and affects the brain and other organs.

Brain

Cellular changes take place in the brain when marijuana, or pot, is smoked. NIDA researchers have found that THC impairs mainly those areas of the brain that produce thoughts, concentration and memory, which are valid reasons to stop smoking pot. Additionally, cannabis influences the pleasure sensors, making it attractive to those with addictive tendencies. Distorted perceptions, difficulty solving problems and poor coordination last for days or weeks after the high wears off. Those who smoke pot daily operate at subpar levels at all times.

Long-term

Over time, the long-term effects on the brain are cumulative, and pot smokers risk brain damage equal to those who take harder drugs like heroin or cocaine. The NIDA says that withdrawal from smoking pot sets up stress centers in the brain that control the brain’s use of dopamine, or pleasure sensors. Addiction to the drug can result from long-term pot smoking. Drug addiction can adversely affect all areas of an addict’s life, including social functioning, work, relationships and hobbies, according to a report from University Health Services at the University of Wisconsin.

Psychological Effects

NIDA studies have shown marked increases in depression, anxiety and suicide in pot smokers. Researchers are not sure whether marijuana use exacerbates an existing mental illness or causes it. Those with violent tendencies or a genetic disposition to psychological problems are more likely to experience mental breakdowns if they smoke pot. The studies NIDA reported have directly linked marijuana use to schizophrenia.

Respiratory System

Smoking pot causes serious damage to the lungs and respiratory system. The NIDA reports that marijuana has 50 to 70 more carcinogens in it than tobacco products do. Deep inhalation of the smoke adds to the level of carcinogens exposed to the lungs. Studies, however, have not been able to link pot smoking with the development of lung cancer. The American Council for Drug Education reports that instead, pot smokers have many of the symptoms of cigarette smokers, including persistent cough, bronchitis, emphysema and other respiratory illnesses.

Heart

When marijuana is inhaled, the heart rate increases by as much as 100 percent. This condition can last for up to four hours after smoking the drug. Pot smokers have a high risk of having a heart attack within one hour of smoking weed, the NIDA reports. Older pot smokers with already weakening cardiac systems are at an even higher risk of heart failure from smoking pot.